During periods of full and intense sun, a greenhouse is naturally heated by the sun's energy and there is very little, if any, need for auxiliary heating. However, at night or during periods of cold, cloudy weather a greenhouse loses its heat quite rapidly and some form of auxiliary heating is therefore required in order to maintain the temperature in the greenhouse at an acceptable level. The soaring cost of fuel for providing auxiliary heating in a greenhouse, and the inability to obtain adequate fuel supplies, has had a severe impact on commercial greenhouse operators, and indeed, has driven a number of greenhouse operators out of business.
The desirability of utilizing solar energy for the heating of homes and other buildings has long been recognized and a number of proposals have been made for applying solar heating technology for the heating of greenhouses. However, the previously proposed or constructed solar heated greenhouses of which applicant is aware have certain limitations or disadvantages which render them impractical or infeasible for application to commercial scale greenhouse.
For example, proposals have been made to provide conventional solar panels adjacent to a greenhouse for collecting solar heat energy to use for heating the greenhouse at night or during cloudy weather. However, because of the expanse of glass and the high heat loss factor of a greenhouse, this type of solar heated greenhouse would require a large number of solar panels and take up a considerable amount of space. The cost and space requirements of such an arrangement is prohibitive.
There have also been proposed a number of designs for a solar heated greenhouse, as for example in recent U.S. Pat. Nos. 4,108,373 and 4,141,498. However, these designs are of an unconventional or exotic construction which are impractical and economically infeasible for application to a commercial scale greenhouse.